The purpose of this project is to test a methodology for measuring unapprehended criminality among heroin users. A total of 1,800 face to face interviews will be undertaken with active and inactive heroin users and non-drug offenders over a 2-year period in Miami and New York. The findings of the study will address the nature and extent of criminal behavior of heroin users as compared to that of non-drug offenders in given areas. Active heroin users include those who are currently in the street community in high density drug use areas and are using heroin at the time of interview. A total of 650 of these subjects will be interviewed. Inactive heroin users include those who are in treatment programs or who are incarcerated. These inactive cases will be restricted to those who are recent admissions (during the past six months) to treatment programs, correctional facilities, or jails, and had been active in the areas under study. The smaller sample of 250 inactive cases will be drawn since they are likely to be a more homogeneous population. This sampling of active and inactive heroin users will permit a comparative analysis to determine if there are differences in the drug use and criminal behavior of officially known cases vs. "hidden" cases. Active non-drug offenders include offenders who are not drug involved, yet are active in the same geographical areas as the heroin users drawn for study. A total of 550 of these subjects will be interviewed. The inactive non-drug offenders will be recently incarcerated offenders (during the last six months), who had been active in the areas under study, and will total 350 subjects. This sampling of four populations will allow comparisons which will indicate any differences in criminal behavior of the given group.